In order to guarantee good quality communications, the network, and possibly the telephone sets (also called IP telephones) must manage the quality of service (QoS) that is to say the monitoring of the IP packet handling time, of the jitter (i.e. the variation in the packet handling time), and of the loss of packets. This management may be carried out either by implementing a specific protocol such as the DiffServ protocol (“Differentiated Services”, RFC 2474 and RFC 2475) which acts at level 3 (network layer of the OSI reference model) by tagging the packets with a priority level, or by implementing a protocol such as the “VLAN Tagging” IEEE 802.1 Q/P standard of the IEEE which acts at level 2 (link layer of the OSI reference model) by tagging the frames with a virtual subnet identifier and a priority level.
Even if the existing devices of the network are compatible with the DiffServ protocol, the tagging of the frames according to the 802.1 Q/P standard is advantageous if the network, for example an Ethernet network (see the IEEE 802.3 standard, taken up at the ISO under the nomenclature ISO 8802.3) already exhibits a structure of virtual subnets, for example of VLAN type (“Virtual Local Area Network”), for the various computer applications. For example, the network can comprise a “data” VLAN for transporting the data streams, and a “telephony” VLAN for transporting the ToIP streams. In this case indeed, each terminal device of the network already tags its frames with a VLAN identifier by employing version 802.1 Q of the standard. It is then sufficient to employ version 802.1 Q/P of the standard in order for an IP telephone to tag its frames with a VLAN identifier and a priority level, this making it possible to guarantee good QoS.
According to the current version of IP (IPv4), in order to operate, a network device requires the following parameters which form what is called a lease and are the subject of a configuration procedure:                a unique address on the network (IP address);        a subnet mask which identifies the IP subnet to which the device belongs from among the whole set of interconnected IP networks; and        the address of the default router with which the device has to communicate (“DeFault Gateway” or DFG).        
Other parameters are available for the specific requirements of applications. In total, there are 63 parameters. This is why the configuring of the devices performed manually during the installation of each of them is onerous, especially in respect of IP telephones which have only a telephone keypad for man/machine interface.
A requirement exists which consists in allowing an IP telephone to automatically receive its IP parameters from a configuration server such as a DHCP (“Dynamic Host Configuration Protocol”, RFC 3361) server at each boot. The term boot is understood to mean physical and/or electrical connection of the device to the network. This in fact makes it possible to simplify the management of the network, in particular the mass deployment of telephone sets on the existing IP network but also their maintenance. Automatic configuration of the IP parameters in fact avoids the need to enter the IP information and the QoS information (i.e., the information specific to DiffServ or to 802.1 Q/P, for example) into the keypad of each telephone set, this information forming the parameters of the lease thereof. Accordingly, the DHCP client of the telephone set asks the DHCP server for these parameters directly with the aid of the “class identifier” field of a lease request. The DHCP server then sends it the parameters with the aid of the “Vendor Specific information” field of a lease offer.
A user's work environment generally comprises an IP telephone and a computing system such as a general-purpose computer (hereinafter PC, standing for “personal computer”). It is therefore necessary to manage the shared utilization of various protocols and standards which are implemented during the booting of the IP telephone or of the PC, namely DHCP, Relay DHCP, IEEE 802.1 Q/P and/or DiffServ, and IEEE 802.3. It is recalled that DHCP allows any IP system to dynamically receive its network configuration from a DHCP server. Relay DHCP, which corresponds to a chapter of DHCP, is a functionality which, when it is employed on IP routers, makes it possible to relay the requests sent by the DHCP clients to a DHCP server connected to a different network (remote network on different WAN or VLAN link). The IEEE 802.1 Q/P standard makes it possible to define virtual subnets and to assign them different processing priorities. DiffServ is a protocol for tagging the priority of an IP frame. Finally, the IEEE 802.3 standard defines the format of Ethernet frames.
When the IP telephone and the PC of one and the same workstation are connected to the IP network by two separate physical access ports, the processing of the protocols and standards is carried out in a completely distinct manner by the active devices of the network. An automatic configuration and QoS virtual subnet policy can therefore be implemented separately for the IP telephone and for the PC.
On the other hand, when using a switch to connect the two devices to the IP network across a single physical access port, the necessary differentiation between the two devices is no longer achievable with the basic functions of the protocols and standards implemented. Such a switch is for example an Ethernet switch having three ports. It is for example integrated within the IP telephone to make it possible to deploy telephony over IP without needing to modify the architecture of an existing network in order to add a physical access port dedicated to telephony for each workstation. Certain problems related to the sequencing of the operations during the booting of the IP telephone may then occur. These problems are related to the specific manner of operation of the DHCP protocol and of the IEEE 802.1 standard. As a result, the IP telephone and the PC receive a lease which is necessarily on the same VLAN. This signifies that the ToIP stream and the data stream are mixed, and are processed with the same priority.
It is therefore desirable to guarantee transparency of operation of the IP telephone which integrates a switch, vis-à-vis the PC which is connected thereto and which is likewise a DHCP client, during the booting of the IP telephone or of the PC, when these devices perform their lease request and when they receive configuration information.
A technology has been proposed by the constructor of Cisco network devices, which relies on the implementation of an additional protocol called CDP (“Cisco Discovery Protocol”). This protocol is entirely proprietary. It is found only on certain Ethernet switches, certain routers and on the IP telephones manufactured by Cisco.
During its booting, the IP telephone uses the CDP protocol to identify itself on the Cisco Ethernet switch. The latter recognizes this type of client and automatically places the subsequent Ethernet frames on the “telephony” VLAN whose number has previously been configured on each of the Ethernet switches of the network.
If a PC is connected to the same physical access port of the Ethernet network by way of said Ethernet switch, the switch automatically differentiates between the two devices based on the MAC (“Media Access Control”) addresses of each of them. The Ethernet frames originating from the PC are directed onto the “data” VLAN, which is typically customized on the port of the switch which receives them, and the frames sent by the IP telephone are broadcast on the “telephony” VLAN. Thus, the whole set of ToIP streams of each IP telephone of the network is located dynamically on a separate VLAN to which the desired priority is applied.
This configuration procedure is admittedly entirely automatic, the priority and VLAN number parameters possibly being configured in a centralized manner by the network administration tool. Nevertheless, the solution is entirely based on a proprietary protocol available only on certain Ethernet switches and Cisco routers (only the most recent ones). In particular the procedure described above no longer operates if the network comprises devices other than those from Cisco.
Moreover, the whole set of IP telephones receives a lease which is necessarily on one and the same “telephony” VLAN. Now, in certain organizations or enterprises, several different “telephony” VLANs are necessary in order to respond to requirements regarding security or isolation of the various telephone subnets. BRIEF DESCRIPTION OF THE INVENTION Accordingly, a first aspect of the invention proposes a method for the automatic configuration of a determined device of a packet switching data transmission network on which are defined at least one first virtual subnet for network devices of a first type and at least one second virtual subnet for network devices of a second type. The device is physically connected to any one of said first and second virtual subnets. It belongs to any one of said first and second types. The method comprises the steps according to which the device performs the steps of:                broadcasting over the virtual subnet to which it is physically connected, a first lease request comprising an identifier of the type to which it belongs;        receiving, in response to said first lease request, a first lease containing an address on the virtual subnet to which it is physically connected, an identifier of the virtual subnet of the devices of the type to which it belongs, and, if it does not belong to the type of the devices of the virtual subnet to which it is connected, a cue for activating tagging of the frames with said virtual subnet identifier;        if said first lease contains said tagging activation cue:        releasing said first lease;        broadcast mode broadcasting over the virtual subnet of the devices of the type to which it belongs, a second lease request tagged with said identifier of the virtual subnet of the devices of the type to which it belongs; and        receiving, in response to said second lease request, a second lease containing an address on the virtual subnet of the devices of the type to which it belongs;        otherwise retaining said first lease.        
A second aspect of the invention relates to a system comprising a packet switching data transmission network on which are defined at least one first virtual subnet for network devices of a first type and at least one second virtual subnet for network devices of a second type. The system furthermore comprises a determined device which is physically connected to any one of said first and second virtual subnets. The device belongs to any one of said first and second types. The device is adapted for implementing a method according to the first aspect.
A third aspect of the invention pertains to a device of a packet switching data transmission network on which are defined at least one first virtual subnet for network devices of a first type and at least one second virtual subnet for network devices of a second type. The device belongs to any one of said first and second types. It comprises means for executing a method according to the first aspect.
The concepts of virtual type of devices and of subnets of the devices of a determined type are nonlimiting. They imply a set of devices that the network administrator may wish to group together on one and the same virtual subnet according to a determined criterion or a combination of determined criteria. For example, a criterion may pertain to the nature of the devices (in particular, the terminal devices or the system devices, respectively for telephony or for data, may be grouped together on distinct virtual subnets). Another criterion may be geographical (all the devices situated in a determined building or a determined local area may be grouped together on one and the same virtual subnet). Another criterion still may be functional (the terminal devices of a group of identified users may be grouped together on one and the same virtual subnet, independently of their geographical position), etc.
The main network is for example a local area network (LAN) with an Ethernet network as backbone. The virtual subnets are for example VLANs. The virtual subnets are for example defined and managed according to the IEEE 802.1 Q/P standard. According to this standard, the first lease proposal furthermore contains a priority number associated with the device. In this case, the second lease request advantageously contains this priority number.
The devices of the first and/or of the second type are for example terminal devices. The devices of the first type are for example PCs, and the devices of the second type are for example IP telephones. Nevertheless the invention may also be implemented on network devices such as ToIP gateways or the like.
The configuration server is for example a DHCP server, that is to say it employs the DHCP configuration protocol. The implementation of the invention is compatible with network architectures serviced by one or more configuration servers.
The first lease request is processed by a first configuration server which is or is not physically connected to the virtual subnet to which the device is physically connected. If it is not, the first lease request in broadcast mode is relayed in uni-recipient mode (“unicast”) to said first configuration server via one or more appropriate routers, such as routers employing the Relay DHCP protocol in the example.
Likewise, the second lease request is processed by said first configuration server or a second configuration server which is or is not physically connected to the devices virtual subnet to which the device belongs. If not, the second lease request in broadcast mode is relayed in uni-recipient mode to said first or second configuration server via one or more appropriate routers.
If it is the same configuration server (i.e., said first configuration server) which services the first and second virtual subnets and processes the first and second lease requests, this configuration server manages a first and a second address range (“scope”) respectively on the first and on the second virtual subnets. In a general manner, it manages an address range for each virtual subnet which it services. Thus, if it is moreover the only configuration server of the network, it manages an address range for each virtual subnet of the network.
The invention is thus advantageously based on the use of normal protocols and standards: IEEE 802.3, IEEE 802.1 Q/P, DHCP and Relay DHCP. It is therefore completely independent of the existing devices on the network.
Each device is configured entirely, and in an entirely dynamic manner, in accordance with the particulars provided by the configuration server (or servers). No additional intervention by the network administrator is required to configure the QoS. The deployment and especially the maintenance of large telephone over IP networks are therefore easier.
The network administrator can establish as many virtual subnets of each type as necessary, by customizing the configuration server(s) alone. Moreover, the modification of the virtual subnets is easy, by modifying the customization of the configuration server(s) without having to intervene on the terminal devices linked to the main network.
The first device and the second device may operate simultaneously as client of the configuration protocol. Despite being connected to the main network by the same physical access port, they receive configuration leases on different virtual subnets and are thus attached to different virtual subnets. Each type of device's own QoS is thus guaranteed.
The use of the existing cabling with a single physical access port, i.e., a single network socket, per user (by virtue of a switch integrated within one of the devices) is thus made possible by separating each type of device's own information streams on distinct virtual subnets, each of which is dynamically configurable.
The implementation of the invention greatly facilitates the mass installation and the maintenance of IP telephones on network infrastructures such as large Ethernet backbones, of the type of those deployed on university campuses or company sites.
Moreover, devices other than terminal devices, such as for example ToIP gateways or the like of the network, may benefit therefrom. The advantages of the invention are, for them, less than for terminal devices since these devices do not integrate any Ethernet switch allowing them to be strung together in a chain with computing devices.